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MOSFET N-type Capacitor a=200

MOSFET N-type Capacitor a=200

VSUB (v) MOSFET N-type Capacitor d=200

MOSFET P-type a=200

MOSFET P-type a=200

MOSFET P-type Capacitor d=200

MOSFET P-type Capacitor d=200

Figure 12. Capacitance versus voltage curves of MOS P- and N-type capacitors (a) N-type square capacitor with size of 200 /m. (b) N-type round capacitor with diameter of 200 /m. (c) P-type square capacitor with size of 200 /m. (d) P-type round capacitor with diameter of 200 /m. Reprinted with permission from [203], F. Hua et al., Nanotech-nology 14, 453 (2003). © 2003, Institute of Physics.

Figure 12. Capacitance versus voltage curves of MOS P- and N-type capacitors (a) N-type square capacitor with size of 200 /m. (b) N-type round capacitor with diameter of 200 /m. (c) P-type square capacitor with size of 200 /m. (d) P-type round capacitor with diameter of 200 /m. Reprinted with permission from [203], F. Hua et al., Nanotech-nology 14, 453 (2003). © 2003, Institute of Physics.

many respects, modification and optimization of the traditional process is required.

During the lift-off, it was better to introduce ultrasonic treatment for 3 seconds when the wafer was soaked in developer solution. Inside the structure of the nanoparticle film, polyion multilayers such as PDDA and PSS were sandwiched between the nanoparticle film and photoresist as a kind of "chemical glue." The structure of the polyion is like a long thread that strongly links one to the other. It is hard to break them up during the lift-off, so at some areas the nano-particle and polyion multilayer cannot be removed when the photoresist is dissolved. They just drop down and reattach to the film underneath, as shown in Figure 9(b). The ultrasonic treatment is introduced to disconnect the linkage between polyion branches and obtain a more distinct pattern with higher reproducibility.

Other dielectric materials, such as montmorillonite, has also been tested as the insulating layer. They did not perform as well as the silica nanoparticle, although the mono-layer thickness can be more precisely controlled. There are many other nanoparticles suitable for LbL self-assembly that may function differently for various devices.

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